Conventionally, a fixing device of a heat roller fixing type has been widely used in an electrophotographic image forming apparatus such as a copying machine and a printer. The fixing device of the heat roller fixing type includes a pair of rollers (a fixing roller and a pressure roller) pressured each other, one or both of which incorporates a halogen heater so as to heat the rollers to a predetermined temperature. The rollers form a nip area (contact area), where a sheet being carried is pressured and heated by the rollers. As a result of the pressure and heat, a non-fixed toner image attached to the sheet is fixed to the sheet.
However, such a fixing device of the heat roller fixing type has involved the following problem. According to the fixing device of the heat roller fixing type, it takes a long time to heat up the fixing roller and the pressure roller so that these rollers are capable of thermal fixing. Therefore, the fixing roller and the pressure roller need to be preheated even in a standby mode. This causes an increase in power consumption.
In order to solve the problem, there has been proposed a laser fixing device which irradiates a laser beam to a non-fixed toner image on a sheet, so that the non-fixed toner image is melted and fixed to the sheet. Such a laser fixing device is disclosed in Patent Literatures 1 and 2. Further, Patent Literature 3 discloses a fixing device which is configured such that only part, of the sheet, where non-fixed toner is positioned is selectively irradiated with the laser beam. Moreover, Patent Literature 4 discloses a fixing device which is configured such that (i) a downstream region of the sheet in a direction in which the sheet is carried and (ii) an upstream region of the sheet in the direction in which the sheet is carried are irradiated with the laser beam so that toner in the downstream region receives a greater amount of heat than toner in the upstream region does.
Citation List
Patent Literatures
Patent Literature 1
Japanese Patent No. 3016685 B (Publication Date: Mar. 6, 2000)
Patent Literature 2
Japanese Patent Application Publication, Tokukai, No. 2005-70536 A (Publication Date: Mar. 17, 2005)
Patent Literature 3
Japanese Patent Application Publication, Tokukaihei, No. 2-221984 A (Publication Date: Sep. 4, 1990)
Patent Literature 4
Japanese Patent Application Publication, Tokukai, No. 2008-89828 A (Publication Date: Apr. 17, 2008)